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Biomedical subjects

T Nambara

Publications and source records attributed to T Nambara.

At least 37 records · Page 2Linked to original sources
PubMed1994

Analysis of conjugated bile acids in human biological fluids. Synthesis of hyodeoxycholic acid 3- and 6-glycosides and related compounds.

The glucuronide, glucoside and N-acetylglucosaminide conjugates of hyodeoxycholic acid were synthesized. In addition, murideoxycholic acid 3-glycosides and some of their C-5 epimeric analogs were also prepared. The principal reactions used are 1) the Koenigs-Knorr condensation reaction of 3-oxo-6 alpha-hydroxy and 6-oxo-3 alpha-hydroxy esters with an appropriate alpha-acetohalosugar catalyzed by cadmium carbonate in benzene under reflux, 2) reduction of the resulting bile acid glycoside methyl ester-acetates with tert-butylamine-borane complex, and 3) subsequent hydrolysis with aqueous lithium hydroxide.

Bile Acids and Salts↗
PubMed1993

Assay of enzymic O-methylation of catechol oestrogens by high-performance liquid chromatography with coulometric detection.

A simple and sensitive method for the determination of guaiaicol oestrogens enzymatically formed from 2- or 4-hydroxyoestradiol, by means of high-performance liquid chromatography with coulometric detection, has been developed. Catechol and guaiacol oestrogens were efficiently separated on a reversed-phase column, using 0.5% ammonium phosphate buffer (pH 3.0)-acetonitrile (59:41, v/v) as the mobile phase, and detected coulometrically in a screening-oxidation mode at +0.10 V and +0.35 V, respectively. The method was applied to the assay of in vitro enzymic O-methylation of catechol oestrogens. After 2- or 4-hydroxyoestradiol had been incubated with rat red blood cells in the presence of S-adenosylmethionine, the resulting guaiacols and unchanged substrate were percolated through an Extrelut-3 cartridge. The dried eluate was redissolved and directly injected. This simple procedure was as sensitive as the previously reported method using gas chromatography-mass spectrometry in a selected ion monitoring mode.

Animals↗
PubMed1993

Enzymatic O-methylation of catechol estrogens in red blood cells: differences in animal species and strains.

Enzymatic O-methylation of catechol estrogens in red blood cells has been investigated with respect to species difference. In the presence of S-adenosylmethionine, 2- or 4-hydroxyestradiol (2-OHE2 or 4-OHE2) was incubated with blood lysate obtained from rats (five strains), guinea pigs, mice, rabbits, dogs, monkeys, and humans, respectively. The yielded guaiacols and unchanged substrate were determined by gas chromatography/mass spectrometry in a selected ion monitoring mode employing the corresponding 2H4-labeled compounds as internal standards. The total amounts of guaiacols formed from 2-OHE2 and 4-OHE2 were different, being the highest (79.6% and 38.1%) in monkeys and the lowest (5.1% and 1.9%) in humans. The ratios of isomeric guaiacols formed from 4-OHE2 (4Me/3Me) were 7.6-71, while those from 2-OHE2 (2Me/3Me) were 1.4-3.2. Thus, marked differences in O-methylation of catechol estrogens were observed among animal species, but no significant strain difference was detected in rats.

Adult↗
PubMed1993

Potential bile acid metabolites. 20. A new synthetic route to stereoisomeric 3,6-dihydroxy- and 6-hydroxy-5 alpha-cholanoic acids.

An improved procedure for the syntheses of stereoisomeric 3,6-dihydroxy- and 6-hydroxy-5 alpha-cholanoic acids (and their methyl esters) is described. The principal reactions employed are those reported in the preceding paper of this series, with the commercially available hyodeoxycholic acid as starting material. The final step in the procedure is the reduction of the key 5 alpha C-6 ketones with either the stereoselective equatorial reagent, Li/NH3/MeOH, or the axial reagent, Zn(BH4)2. The results of analysis of the prepared 6-monohydroxylated and 3,6-dihydroxylated stereoisomers by thin-layer chromatographic, high performance liquid chromatographic and gas-liquid chromatographic mobilities, and 1H and 13C nuclear magnetic resonance spectra are discussed along with the data for the corresponding compounds in the 5 beta-series.

Bile Acids and Salts↗
PubMed1993

Potential bile acid metabolites. 19. The epimeric 3 alpha,6,7 beta-trihydroxy- and 3 alpha,6,7 beta,12 alpha-tetrahydroxy-5 alpha-cholanoic acids.

Syntheses by a new procedure of the known 3 alpha,6 alpha,7 beta- and 3 alpha,6 beta,7 beta-trihydroxy-5 alpha-cholanoic acids, and of the once-reported analog 3 alpha,6 alpha,7 beta,12 alpha-, as well as the new 3 alpha,6 beta,7 beta,12 alpha-tetrahydroxy-5 alpha-cholanoic acids, are described. Key intermediates of the syntheses are the 6-oxo-7 beta-ols of the respective 5 alpha-cholanoic acids (and their methyl esters) prepared by allomerization at C-5 of appropriate 6-bromo-7-oxo derivatives of the corresponding 5 beta-acids. Successful reduction of the 6,7-ketols to the desired products depended on the proper choice of reagents, either Zn(BH4)2 or Li/NH3/MeOH.

Ammonia↗
PubMed1993

Enzyme immunoassay for 4-hydroxy-2-(4-methylphenyl)benzothiazole.

A specific enzyme immunoassay (EIA) has been developed for 4-hydroxy-2-(4-methylphenyl)benzothiazole (KB-2714) (1), an active metabolite of 4-acetoxy-2-(4-methylphenyl)benzothiazole (KB-2683) (2) which is a promising anti-rheumatic agent. The EIA was based upon antiserum elicited against 5-(2-carboxyphenylazo)-4-hydroxy-2-(4-methylphenyl)benzothiazole (3)-bovine serum albumin conjugate and beta-galactosidase-labelled 5-amino-4-hydroxy-2-(4-methylphenyl)benzothiazole (5). The sensitivity of the EIA was significantly improved by the utilization of a bridge heterologous combination system. An appropriate dose-response curve of EIA for 4-hydroxy-2-(4-methylphenyl)benzothiazole was obtained in the range of 10 pg tube-1-20 ng tube-1. The specificity of EIA proved to be satisfactory in terms of cross-reactivities to 14 benzothiazole-related compounds including glucuronic acid and sulphuric acid conjugates. The proposed method was evaluated to be useful for the determination of 1 in urine and plasma with acceptable recovery and inter- and intra-assay precision.

Antigens↗
PubMed1992

Studies on steroids. CCLIV. Gas chromatographic-mass spectrometric determination of 4- and 6-hydroxylated bile acids in human urine with negative ion chemical ionization detection.

A method for the determination of 4- and 6-hydroxylated bile acids with a vicinal glycol moiety in human urine by gas chromatography-mass spectrometry with negative ion chemical ionization detection is described. The 4 beta-hydroxylated bile acids labelled with 18O and 2H were prepared as internal standards by the exchange reaction of the carbonyl group on the steroid nucleus with H2(18)O, followed by metal deuteride reduction. Bile acids in urine were extracted with a Sep-Pak C18 cartridge and, after solvolysis and hydrolysis of the conjugated forms, transformed into pentafluorobenzyl ester diethylhydrogensilyl ether diethylsilylene derivatives. Subsequent resolution into individual 4- and 6-hydroxylated bile acids was carried out on a cross-linked fused-silica capillary column; a characteristic carboxylate anion, [M-PFB]-, was used to monitor each bile acid in the negative ion mode. The newly developed method was applied to the separation and determination of 4- and 6-hydroxylated bile acids in a urine specimen from a newborn infant.

Bile Acids and Salts↗
PubMed1992

Synthesis of N-acetylglucosaminides of unconjugated and conjugated bile acids.

3-N-Acetylglucosaminides of unconjugated, glycine- and taurine-conjugated bile acids have been synthesized. Bile acids appropriately protected were condensed with acetochloroglucosamine through the 3 alpha-hydroxyl group by means of the Koenigs-Knorr reaction using cadmium carbonate as a catalyst. Subsequent borohydride reduction and/or alkaline hydrolysis provided desired 3-N-acetylglucosaminides of unconjugated bile acids. Glycine-conjugates were obtained from N-acetylglucosaminides of unconjugated bile acids and ethyl glycinate by the carbodiimide method. The preparation of N-acetylglucosaminides of taurine-conjugates was attained by the Koenigs-Knorr reaction of bile acid p-nitrophenyl esters followed by condensation with taurine. 7-N-Acetylglucosaminides of ursodeoxycholates were prepared in a similar fashion. The convenient synthesis of 3-N-acetylglucosaminides of unconjugated bile acids is also described.

Acetylglucosamine↗
PubMed1992

7-Oxodihydrokarounidiol [7-oxo-D:C-friedo-olean-8-ene-3 alpha,29-diol], a novel triterpene from Trichosanthes kirilowii.

The structure of 7-oxodihydrokarounidiol [7-oxo-D:C-friedo-olean-8-ene-3 alpha,29-diol], isolates from the seeds of Trichosanthes kirilowii (Cucurbitaceae), was determined by chemical correlation with karounidiol [D:C-friedo-oleana-7,9(11)-diene-3 alpha,29-diol] from the same source. Two other natural products, viz. bryonolic acid (3 beta-hydroxy-D:C-friedo-olean-8-en-29-oic acid) and bryononic acid (3-oxo-D:C-friedo-olean-8-en-29-oic acid), were also correlated with karounidiol.

Magnetic Resonance Spectroscopy↗
PubMed1991

Studies on steroids. CCLIII. Capillary gas chromatographic behaviour of diethylhydrogensilyl-diethylsilylene derivatives of stereoisomeric bile acids.

The capillary gas chromatographic behaviour of diethylhydrogensilyl (DEHS) ethers and/or diethylsilylene (DES) derivatives of fifty bile acids including 4- and 6-hydroxylated compounds is described. The methylene unit (MU) values of methyl and pentafluorobenzyl esters of bile acids were determined as their trimethylsilyl (TMS), dimethylethylsilyl (DMES) ethers and DEHS-DES derivatives. The differences in methylene unit values between the corresponding TMS ethers and DMES ethers or DEHS-DES derivatives were used for estimating the number and stereochemistry of hydroxyl groups on the steroid nucleus. On treatment with the silylating agent N,O-bis (diethylhydrogensilyl)trifluoroacetamide, bile acids possessing isolated hydroxyl in addition to diaxial trans-glycol groups were easily converted into the DEHS ehters, whereas those having a vicinal glycol group except for the diaxial group were converted into cyclic DES derivatives. The mass spectrometric properties obtained with negative-ion chemical ionization detection are discussed.

Bile Acids and Salts↗
PubMed1991

Studies on steroids. CCLII. Separation and characterization of 3-oxobile acids in serum by high-performance liquid chromatography with fluorescence detection.

The separation of unconjugated and glycine- and taurine-conjugated bile acids with a C-3 oxo group has been carried out by high-performance liquid chromatography on a reversed-phase column. The chromatographic behaviour of these 3-oxobile acids was dependent on the number and positions of hydroxyl groups and the structure of the side-chain. The newly developed method has been applied to the characterization of 3-oxobile acids in biological fluids. The bile acid fraction was obtained from a serum specimen by passing it through a Sep-Pak C18 cartridge. 3-Oxobile acids were derivatized quantitatively to fluorescent oximes through the oxo group by treatment with O-(2-anthrylmethyl)hydroxylamine. The derivatives were separated into the unconjugated and glycine- and taurine-conjugated fractions by ion-exchange chromatography on a lipophilic gel, piperidinohydroxypropyl Sephadex LH-20. Subsequent resolution of each fraction into individual 3-oxobile acids was achieved by chromatography on a Nova-Pak Phenyl column using 3% methanol in 0.3% potassium phosphate buffer (pH 7.0)-acetonitrile (8:5, v/v) as the mobile phase. The derivatized 3-oxobile acids were monitored by fluorescence detection (excitation wavelength 260 nm and emission wavelength 405 nm), the limit of detection being 20 fmol. Glycine- and taurine-conjugated 7 alpha,12 alpha-dihydroxy- and 7 alpha-hydroxy-3-oxo-5 beta-cholanoic acids in human serum were unambiguously idenitified on the basis of their chromatographic behaviour using mobile phases of different pH values.

Bile Acids and Salts↗
PubMed1991

Potential bile acid metabolites. 17. Synthesis of 2 beta-hydroxylated bile acids.

The 2 beta-hydroxylated derivatives of lithocholic, chenodeoxycholic, deoxycholic, and cholic acids were synthesized from the respective parent bile acids by established procedures. The principal reactions involved were (1) bromination of 3-oxo formylated bile acids in N,N-dimethylformamide, (2) rearrangement and substitution of the resulting 4 beta-bromo-3-oxo derivatives to the 2 beta-acetoxy-3-oxo compounds with potassium acetate, and (3) reduction to the 2 beta-acetoxy-3 alpha-hydroxy compounds with tert-butylamine-borane complex. As for the prepared 2 beta-hydroxylated bile acids with a diequatorial trans-glycol structure, proton and carbon-13 nuclear magnetic resonance spectroscopic and gas-liquid chromatographic/mass spectrometric properties are discussed.

Acetates↗
PubMed1991

Structure of the adduct of 16 alpha-hydroxyestrone with a primary amine: evidence for the Heyns rearrangement of steroidal D-ring alpha-hydroxyimines.

16 alpha-Hydroxyestrone, a product of estrogen 16 alpha-hydroxylation in humans that is suspected to be implicated in cell transformation, has been found to form stable adducts with nuclear components. The stable covalent adduct formed from 16 alpha-hydroxyestrone with 2-methoxyethylamine via the Heyns rearrangement of the alpha-hydroxyimine was identified as 3-hydroxy-17 beta-(2-methoxyethylamino)estra-1,3,5(10)-trien-16-one. Since the same product was obtained from 16 beta-hydroxyestrone with the amine, the alpha-hydroxyenamine is the most likely intermediate of the Heyns rearrangement. The adduct was fairly stable at 37 C in phosphate buffer (pH 7.4)/methanol (1:1 v/v), while the adduct formed from 16-oxoestradiol was disrupted reversely and completely within 6 hours. The evidence suggests that N-(3-hydroxy-16-oxoestra-1,3,5(10-trien-17 beta-yl)amine is the partial structure of the stable adducts formed from D-ring alpha-ketol estrogens with proteins.

Amines↗
PubMed1991

Enzyme immunoassay for (3-amino-1-methyl-5H-pyrido[4,3-b]indole), a tryptophan pyrolysate.

For evaluation of the cancer risk by the tryptophan pyrolysates a sensitive enzyme immunoassay for 3-amino-1-methyl-5H-pyrido-[4,3-b]indole (Trp-P-2), a mutagenic and carcinogenic substance, found in foods and biological fluids has been developed. The dose-response curve obtained was suitable for the determination of Trp-P-2 in the range of 20-800 pg. The immunoassay system was characterized to be satisfactorily specific as judged by cross-reactivity to gamma-carboline derivatives and their precursors, and comparison of immunoreactive Trp-P-2 levels in the basic and neutral fraction derived from pyrolyzed amino acids and related compounds.

Carbolines↗
PubMed1991

Chemical conversion of corticosteroids to 3 alpha,5 alpha-tetrahydro derivatives. Synthesis of 5 alpha-cortol 3-glucuronides and 5 alpha-cortolone 3-glucuronides.

The synthesis of the 3-glucuronides of 5 alpha-cortol-20 alpha, 5 alpha-cortolone-20 alpha and their 20 beta-epimers is described. The 5 alpha-cortol 20,21-diacetates (12, 17) and 5 alpha-cortolone 20,21-diacetates (14, 19) were the key intermediates. Sodium borohydride reduction of the carbonyl group at C-20 in 5 alpha-tetrahydrocortisol 3-tert-butyldimethylsilyl ether 17,21-acetonide (8) gave the 20 alpha-hydroxy-acetonide (9). Selective removal of the acetonide ring was successful when the 20 alpha-acetoxy-17 alpha,21-acetonide (10) was treated with 50% acetic acid. Subsequent acetylation with acetic anhydride in pyridine, followed by removal of the protecting group at C-3 in the silyl ether-acetate (11) gave the desired 20 alpha-intermediate (12). The 11-ketone (14) was prepared from 11 by oxidation with pyridinium chlorochromate, followed by desilylation. The 20 beta-acetates (17, 19) were synthesized from 21-acetoxy-3 alpha,11 beta,17 alpha-trihydroxy-5 alpha-pregnan-20-one 3-tert-butyldimethylsilyl ether (15). Introduction of the glucuronyl residue at C-3 was carried out by means of the Koenigs-Knorr reaction.

Adrenal Cortex Hormones↗
PubMed1991

Potential bile acid metabolites. XVIII. Synthesis of stereoisomeric 3,6,12 alpha-trihydroxy-5 beta-cholanoic acids.

Two new 6-hydroxylated bile acids, 3 beta, 6 alpha, 12 alpha- and 3 beta, 6 beta, 12 alpha-trihydroxy-5 beta-cholanoic acids, were synthesized from deoxycholic acid. In addition, their C-3 epimers, 3 alpha, 6 alpha, 12 alpha- and 3 alpha, 6 beta, 12 alpha-trihydroxy acids, were prepared by a new route. The principal reactions used were 1) 6 beta-hydroxylation of 3-methoxy-3,5-dienes with m-chloroperbenzoic acid in aqueous dioxane; 2) catalytic hydrogenation of the resulting 6 beta-hydroxy-3-oxo-4-enes to the 6 beta-hydroxy-3-oxo-5 beta compounds with palladium on calcium carbonate catalyst in ethanol; and 3) stereoselective reduction of appropriate 3-oxo derivatives with potassium tri-sec-butylborohydride and tert-butylamine-borane complex. The thin-layer chromatographic, gas-liquid chromatographic, and high performance liquid chromatographic mobilities, and 1H- and 13C-nuclear magnetic resonance spectroscopic data of the four stereoisomers are presented. With this work all the 6-hydroxylated derivatives of lithocholic, deoxycholic, chenodeoxycholic, ursodeoxycholic, and cholic acids in the 5 beta series are now known and have been synthesized.

Bile Acids and Salts↗
PubMed1990

Multiplicity of in vitro glucuronidation of 2-hydroxyestriol.

In vitro glucuronidation of 2-hydroxyestriol has been investigated by means of HPLC with dual-electrode coulometric detection. When incubated with rat or dog liver microsomal preparation in the presence of UDPGA, 2-hydroxyestriol was transformed into the 2-glucuronide together with a small amount of 16- and/or 17-glucuronides. In contrast, incubation of 2-hydroxyestriol with guinea-pig liver microsomal preparation yielded the 3-glucuronide and a trace amount of the 2-glucuronide, but no ring D glucuronides. Upon pretreatment with 3-methylcholanthrene male rat liver exhibited a marked increase in both 2- and 3-glucuronidation activities, whereas female rat liver showed an elevation only in 2-glucuronidation. On the other hand, in male and female rats pretreatment with phenobarbital caused a relatively small increase in the glucuronidation activity of the liver. In the male guinea-pig, glucuronidation was not affected by pretreatment with either of the two compounds. The present result demonstrates the multiplicity of hepatic 2-hydroxyestriol UDP-glucuronyl-transferase in the rat, guinea-pig and dog.

Animals↗